Re: Accelerometer/INS question

From: Henry Spencer (henry_at_spsystems.net)
Date: 06/29/04 

Date: Tue, 29 Jun 2004 01:00:42 GMT

In article <eb01e01d83tsjuhbpovdmg6sd79mgeoekf@4ax.com>,
 <pbreed@netburner.com> wrote:
>Both MEMS devices are good enough for in atmosphere flight where you
>can use GPS and the gravity vector to remove the errors.
>You can assume that the 1Gee gravity vector is aways there
>(or will return shortly after brief periods of non 1 G)

Unfortunately, it's perfectly possible to have a nice clean 1G while the
aircraft is doing something very unpleasant and imminently fatal. In
flight in the atmosphere, what an accelerometer is measuring is the lift
imparted by the wings, **NOT** the gravity vector. (This is why a good
airliner pilot -- or a good airliner autopilot -- can do a substantial
turn, banked to a fair angle, without spilling your drink. The drink is
responding to lift, not gravity.) 

-- 
"Think outside the box -- the box isn't our friend."    |   Henry Spencer
                                -- George Herbert       | henry@spsystems.net